Review and Measurements of Benchmark AHB2 Amp

[AudioAntiRealist]

There are no proofs, science nor facts; only what one decides to believe

Sounds like something someone who studies philosophy might say — I support this

 

[RichB]

May be too late... I still think, painful as it may be, the review threads should be locked and a separate discussion thread created. This has devolved into a pissing contest irrelevant to the AHB2 review itself.

I'd rather keep the thread open for new users and reviews and remove the dross.

- Rich

 

[RichB]

The AHB2 has now been tested in the German trade magazine STEREO 8/2022 and has scored quite well. However, the performance data in bridge mode could not be reproduced. Unfortunately, there are no further details on this.
Here is the measured DF at 4ohms (not bridged), which I have not seen anywhere before (63Hz/1kHz/14kHz): 48/45/19

Do you have a link to the measurements?

- Rich

 

[pogo]

Do you have a link to the measurements?

All measured values will be found here soon, also from the LA4:
Link

 

[Danonano56]

Thoughts and prayers to Benchmark's Siau family as he lost some family members to a terrible tragedy. news article

 

[elvisizer]

holy crap that's AWFUL

 

[DonH56]

See specific thread: https://www.audiosciencereview.com/forum/index.php?threads/john-siau.35908/#post-1255914

 

[JohnM-73]

I’ve literally just purchased a used AHB2, and came here to peruse this thread, and just saw the news. Words can’t express how shocked and sorry I feel for Mr Siau and his family & friends. Thoughts and prayers sent X

 

[Deleted member 49933]

I don't get It. Yes, this thing can push 500 W bridged, but if you just need 100 W for max continuous, then the X8500HA has better power/distortion ratio.

@amirm
0.003% Is -50, not -90.

 

[yanm]

I don't get It. Yes, this thing can push 500 W bridged, but if you just need 100 W for max continuous, then the X8500HA has better power/distortion ratio.

@amirm
0.003% Is -50, not -90.

But 0.003% is -90dB see e.g., http://www.sengpielaudio.com/calculator-thd.htm ( Don‘t forget that one percent is already -40dB ). In addition, the AHB2 THD+N is about or better than 0.0002% for >10W output power…

Now, it is well possible that there will be little audible difference between the X8500HA and the AHB2. When I switched from the internal amplifiers of my MRX 720 to the AHB2 to drive my mains, there was no day-and-night difference (the only objective difference I noticed was when running the room correction program: a trough at the crossover frequency of my loudspeakers went away with the AHB2 - the AVR had likely trouble to drive my speakers as this trough has been very consistent beforehand). Not hearing difference is kind of expected as my loudspeakers have distortions in the -50 to -60dB range, which would mask much lower distortions prior in the audio chain.

On the other hand, my power consumption when listening to music has reduced by about 40W as I now fully bypass the AVR (movie watching has increased by 20W though). In addition, I know that my audio chain up to the loudspeakers is close to SOTA, which likely influence positively my enjoyment of music (psychoacoustic is a real thing).

(edit: typo corrections)

 

[peng]

On the other hand, my power consumption when listening to music has reduced by about 40W as I now fully bypass the AVR (movie watching has increased by 20W though).

(edit: typo corrections)

How would you know that? Did you use something like the Kill-A-Watt plug or you measured the voltage and current separately, or with a wattmeter?
Also, is the 40 W reduction when listening to music for 2 channel stereo and is for peak values (seem very high if that's average value)? Thank you.

 

[yanm]

How would you know that? Did you use something like the Kill-A-Watt plug or you measured the voltage and current separately, or with a wattmeter?
Also, is the 40 W reduction when listening to music for 2 channel stereo and is for peak values (seem very high if that's average value)? Thank you.

I have a smart plug to control my audio-video equipment cabinet. It also measures the total power consumption. There is a base load of about 20W (cable modem/router). I've to disaggregate the loads "by hand" so the per-load accuracy is likely not very good

When listening music with the AVR (2-channel stereo, TV off, no external amplification), the total average power consumption of the cabinet was around 90-100W if memory serves (with external amplification, it is now around 115W).

When listening through the AHB2 and a dedicated streamer (Bluesound Node) and external DAC (Topping E50), the total average power consumption is 48W (pretty constant during the last hour or so). Discounting the base load, the music gear accounts for only 28W: I guess 20-23W for the AHB2, the rest for the streamer and the DAC.

My 40W reduction stems from 90W down to about 48W… the AVR per se consumes more like 70-80W in average (in 2-channel stereo and with video stream off): its amplification channels are always biased even if not used (cannot turn them off without turning off the pre-out AFAIK) and, then, HDMI and DSP chips consume a fair bit of power.

Hopefully that clarifies things.

 

[Deleted member 49933]

But 0.003% is -90dB see e.g., http://www.sengpielaudio.com/calculator-thd.htm ( Don‘t forget that one percent is already -40dB ). In addition, the AHB2 THD+N is about or better than 0.0002% for >10W output power…

I used the main calculator and forgot to add a couple of zeroes.

 

[pogo]

The AHB2 has now been tested in the German trade magazine STEREO 8/2022 and has scored quite well. However, the performance data in bridge mode could not be reproduced. Unfortunately, there are no further details on this.
Here is the measured DF at 4ohms (not bridged), which I have not seen anywhere before (63Hz/1kHz/14kHz): 48/45/19

The measurement data have now been posted online: Link

 

[MC_RME]

Their measurements indicate that their load is not fit for the task - neither is their measurement equipment. And without even saying what they could achieve in bridged mode this looks more like an attempt to keep their usual advertizers happy...

I for one had no problem (except for getting better loads first) to reproduce @amirm 's stellar results with my own AHB2.

 

[SIY]

Their measurements indicate that their load is not fit for the task - neither is their measurement equipment. And without even saying what they could achieve in bridged mode this looks more like an attempt to keep their usual advertizers happy...

I for one had no problem (except for getting better loads first) to reproduce @amirm 's stellar results with my own AHB2.

But it got 93 points. NINETY THREE POINTS! Isn't that enough for you people???!!!!

 

[restorer-john]

@amirm
0.003% Is -50, not -90.

-50dB is 0.3%... Percent is a factor of 100.

Amir is correct.

 

[Paradigm5h1f7]

Well well... this amp uses a feed forward class D power section with a class A output section. It is essentially repackaged BASH technology. Very interesting. Looks like they are starting to re use that old tech since the patent expired!

 

[John_Siau]

Well well... this amp uses a feed forward class D power section with a class A output section. It is essentially repackaged BASH technology. Very interesting. Looks like they are starting to re use that old tech since the patent expired!

The above is incorrect.

The AHB2 has a class-A/B output section with dual bipolar output rails (class-G). A class-A correction amplifier provides feed-forward correction. The main amplifier and correction amplifier are passively summed at the output.

 

[Paradigm5h1f7]

The above is incorrect.

The AHB2 has a class-A/B output section with dual bipolar output rails (class-G). A class-A correction amplifier provides feed-forward correction. The main amplifier and correction amplifier are passively summed at the output.

No no... my apologies... you are reading my statement wrong and need to understand what BASH is in order to understand what they are doing in this amplifier.

Rather then using a large transformer for the INPUT power, they are using a CLASS D style PWM variable rail voltage which changes the input voltage to the transistors depending on the demands of the music input source. The CLASS D section is not used to play music, it is used to provide the rail voltage to the A, A/B music section.

It is, in all senses of the word, an infinitely variable CLASS H amplifier, meaning the voltage power feed is highly flexible on the rails of the A/B amps. The CLASS D power section allows for small voltages at the amplifier during small musical sections, and larger voltages when the music scales up. This means low noise, Class D efficiency, A/B sound.

A feedforward system makes sure the voltage stays above the musical source power requirements.

This is OLD tech, 20 years old, which was patented by a Canadian company. The patent recently expired. At leas this is what this statement is implying on their site.

"On the basis of these characteristics, the AHB2 resembles many class-D switching amplifiers. But make no mistake, the AHB2 is not a class-D amplifier! The AHB2 is a linear class-H amplifier with bipolar output transistors and a unique feedforward error-correction system." BENCHMARK WEBSITE